Leveling devices have long been used by various users, such as, carpenters, brick-layers, plumbers, archers, hunters, to name a few. Each levelling device might be different, however, each level serves to find a horizontal line or plane by means of a bubble in a nonfreezing liquid, usually, mineral spirits, such that by adjustment of the horizontal movement of the bubble to the center of a glass tube that is slightly bowed up from the horizontal longitudinally, one can find a horizontal line or plane.
The leveling devices have also been used with other instruments, such as, sextants and octants, on artillery pieces, and on various industrial equipment, which must all be leveled, and reading the levelling device has sometimes been a most difficult problem.
Oftentimes, the levelling device or the equipment incorporating the leveling device is in an area which is provided with poor lighting, or the levelling is done during a time when natural lighting is poor.
The leveling devices are both manual and electronic, and the leveling devices are both illuminated and non-illuminated. However, this invention is directed to both illuminated and non-illuminated leveling device.
U.S. Pat. No. 4,407,075 (MacDermott) discloses a tubular-shaped spirit vial which is capable of being illuminated at its ends.
U.S. Pat. No. 4,484,393 (LaFreniere) discloses an illuminated spirit level, where a bubble tube is mounted in a support body with light source shielded to define two lights paths directed through the bubble tube to apertures on the outside of the support body so that with the bubble positioned centrally the light is communicated directly from the light source through the bubble tube to the apertures.
U.S. Pat. No. 5,025,567 (McWilliams) discloses an illuminated spirit level containing fiber optic cables for the transmission of light from the self contained light source to the level vials.
U.S. Pat. No. 5,020,232 (Whiteford) discloses a bubble vial of a carpenter's level that is individually illuminated by a light emitting diode (LED) energized from a battery supported with the body of the carpenter's level.
Thus there is a need for a more accurate mechanical leveling device.